This invention relates to a mold for casting ceramic material in slip form and particularly, although not exclusively, for casting articles of sanitary ware of vitreous china.
Traditionally, a seat is a portable carrier quite separate from the mold for use when the mold is opened, the seat being positioned against or under the article which is then shifted by moving the article or the mold part against which the article rests, so that its weight is taken by the seat. The article can then be lifted clear of the mold and left to stand on the seat while it dries. Commonly, seats were made of plaster, wood or other durable, lightweight material.
It has been proposed to adapt one of the mold parts itself to serve as a seat so that the article is lifted away, after casting, on that mold part but hitherto it has been thought that it was necessary always to make all the mold parts, including the one to serve as a seat, from plaster since all the mold parts which have surfaces which define part of the casting cavity must be capable of shaping the article. Thus, when ceramic slip is introduced into the mold cavity, moisture is absorbed from the slip into the plaster of the mold parts, the ceramic material thereby casting up against the inside surfaces of the casting cavity. Sometimes a plug of non-casting material is included in the mold cavity, or a portion of the casting surface can be coated with a resin, to prevent casting in that region, but this has been done only to avoid casting up of the slip at a region of the article where a hole or other opening is to be formed.